[jdk11u-dev] RFR: 8293998: [PPC64] JfrGetCallTrace: assert(_pc != nullptr) failed: must have PC

[Martin Doerr]

Backport of JDK-8293998. Version from 17u-dev applies cleanly, but I've replaced `nullptr` by `NULL` because 11u-dev uses an older C++ standard.

-------------

Commit messages:
 - Backport 90cc8ac9398ff300f6d74383ea84fd82552f1c5d

Changes: https://git.openjdk.org/jdk11u-dev/pull/1390/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk11u-dev&pr=1390&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8293998
  Stats: 76 lines in 2 files changed: 65 ins; 1 del; 10 mod
  Patch: https://git.openjdk.org/jdk11u-dev/pull/1390.diff
  Fetch: git fetch https://git.openjdk.org/jdk11u-dev pull/1390/head:pull/1390

PR: https://git.openjdk.org/jdk11u-dev/pull/1390